Various techniques have been proposed to automatically allow a motor vehicle such as an automobile to warm up or to automatically cool or warm the passenger compartment of the motor vehicle before the driver gets into the motor vehicle especially when the weather is cold or hot.
Japanese Laid-Open Patent Publication No. 55-148739 discloses an automatic warming-up device which includes a timer for starting the engine of an automobile to get it warm several minutes before a certain desired time to start the automobile in motion, particularly in a cold winter morning. When the driver enters the automobile at the desired starting time, the automobile has already warmed up, and hence can immediately be moved.
If the time to start the automobile is changed, however, the driver has to go to a parking lot where the automobile is parked, and to set the timer again to a new starting time.
Another system includes a remote control unit installed at a suitable location in an automobile and a radio control unit for operating the remote control unit. The remote control unit can be operated by a control signal transmitted from the radio control unit. With this system combined with the above automatic warming-up device of the automobile, the driver does not have to go to the parking lot to set the timer again. The system may also be hooked up with various devices in an automobile to control these devices. For example, various lights of the automobile may be controlled by the system so that they can later be turned off under remote control when the driver forgot to turn them off or is not sure if they were turned off when the automobile was parked. The doors of the automobile may be locked by the remote control system when the driver forgot to lock them or is not sure if they were locked at the time the driver left the parked automobile. The driver may instruct the remote control system to get on the handbrake when the driver forgot to pull the handbrake or is not sure if the handbrake was on in the parked automobile.
The above remote control system is however disadvantageous in that it is expensive since both the remote control unit and the radio control unit are manufactured, and considerations have to be given to the radio law and regulations.
Automobile radio telephone units are currently in use as an automobile-mounted device as disclosed in Japanese Laid-Open Utility Model Publication No. 61-195661. Such automobile radio telephone units employ pushbutton dialing as with ordinary telephone units for both signal transmission and reception. An automobile radio telephone unit moves with an automobile in which it is mounted, and transmits and receives a call through a nearby radio station.
The user of an automobile radio telephone unit often finds it difficult to dial the telephone number of a party to be called through the pushbutton dialing system within the vibrating automobile as it runs. Therefore, there is a demand for an automobile radio telephone unit which can be operated more simply and reliably. An automobile radio telephone unit is necessarily equipped with a tracking device which transmits a radio wave to indicate the location of the automobile radio telephone unit at all times in order to determine a radio station which is to be used when receiving an incoming signal Since the tracking device is indispensable, the entire automobile radio telephone system is complex and highly costly.
Recently, personal radio paging units have widely been used which receive a radio signal transmitted from an ordinary telephone unit to summon the person carrying the paging unit. Ordinary personal radio paging units generate a buzzer sound in response to a radio signal received.
Japanese Laid-Open Patent Publication No. 55-133149 discloses a mobile message communication system employing a personal radio paging unit. In the disclosed system, an encoded message is transmitted to the personal radio paging unit, which receives, stores, decodes, and displays or reproduces the message as a voice sound.
According to a selective paging unit or personal radio paging unit disclosed in Japanese Patent Publication No. 59-3839, a signal for calling the person carrying the unit is produced as an acoustic sound, and if there are a number of persons calling the person carrying the unit, some pieces of information for identifying the calling persons such as the names or telephone numbers are displayed on a display screen on the paging unit. The information is however displayed on the display screen on the paging unit for a limited period of time. If the paging unit is carried by the driver of a motor vehicle such as an automobile, the driver may find it difficult to confirm the displayed information or may fail to catch the calling sound while driving the automobile. Where there are a plurality of calling parties, the driver may forget who called him and when the calls came.